1. Field of the Invention
The present invention relates to a semiconductor device and a method of fabricating the same, and in particular, to a semiconductor device comprising a ferroelectric memory employing a highly ferroelectric film as a capacitive insulator and a method of fabricating the same.
2. Description of the Related Art
In recent years, attention has been focused on a semiconductor memory called a FeRAM (Ferroelectric Random Access Memory) comprising a capacitor that employs a ferroelectric film for a capacitive insulator, as the coming generation of a nonvolatile memory.
With a conventional ferroelectric memory, a ferroelectric capacitor comprising a capacitive insulator made up of a ferroelectric film, and an upper electrode and a lower electrode with the capacitive insulator interposed between the electrodes is formed on a semiconductor substrate with an integrated circuit comprising transistors and so froth, formed thereon.
Further, a silicon oxide film serving as an interlayer insulator is formed on top of the semiconductor substrate and the ferroelectric capacitor, and after removal of water constituents contained in the interlayer insulator by heat treatment, contact holes reaching the integrated circuit or the ferroelectric capacitor, provided on the semiconductor substrate, are formed in the interlayer insulator.
A metal pattern made of material such as aluminum (Al), titanium (Ti), or tungsten (W), and so forth is formed inside these contact holes, and is electrically connected to the integrated circuit and the ferroelectric capacitor, respectively. Further, a passivation film serving as a protection film is formed on the respective metal patterns.
With a capacitor making up a conventional FeRAM, an insulating film made of a metal oxide such as strontium bismuth tantalate (SrBi2Ta2O9) called as SBT, lead zirconate titanate (Pb(Zr, Ti)O3) called as PZT, and so forth is used for a capacitive insulator made up of a ferroelectric film.
Further, a noble metal is generally used as the constituent material of the upper electrode and lower electrode. This is because at the time of forming a highly ferroelectric film, and at the time of improving the film quality of the capacitive insulator after the formation of the capacitor, the electrodes making up the capacitor come to be exposed to a high temperature oxidizing atmosphere, so that oxidation resistance is highly required of the constituent material of the electrodes. Particularly, in the case of the conventional ferroelectric capacitor, platinum (Pt) is used as a constituent material of the electrodes from the viewpoint of cost, process stability, ease in the fabrication of the ferroelectric film, and excellent workability.